util_filter.h revision 435c423bdcfa61ff871a9e289d1140f2bac839b8
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#ifndef AP_FILTER_H
#define AP_FILTER_H
#include "apr.h"
#include "apr_buckets.h"
#include "httpd.h"
#include <stdarg.h>
#endif
#ifdef __cplusplus
extern "C" {
#endif
/**
* @file util_filter.h
* @brief Apache filter library
*/
/** Returned by the bottom-most filter if no data was written.
* @see ap_pass_brigade(). */
#define AP_NOBODY_WROTE -1
/** Returned by the bottom-most filter if no data was read.
* @see ap_get_brigade(). */
#define AP_NOBODY_READ -2
/** Returned when?? @bug find out when! */
#define AP_FILTER_ERROR -3
/**
* input filtering modes
*/
typedef enum {
/** The filter should return at most readbytes data. */
/** The filter should return at most one line of CRLF data.
* (If a potential line is too long or no CRLF is found, the
* filter may return partial data).
*/
/** The filter should implicitly eat any CRLF pairs that it sees. */
/** The filter read should be treated as speculative and any returned
* data should be stored for later retrieval in another mode. */
/** The filter read should be exhaustive and read until it can not
* read any more.
* Use this mode with extreme caution.
*/
/** The filter should initialize the connection if needed,
* NNTP or FTP over SSL for example.
*/
/**
* @defgroup filter FILTER CHAIN
*
* Filters operate using a "chaining" mechanism. The filters are chained
* together into a sequence. When output is generated, it is passed through
* each of the filters on this chain, until it reaches the end (or "bottom")
* and is placed onto the network.
*
* The top of the chain, the code generating the output, is typically called
* a "content generator." The content generator's output is fed into the
* filter chain using the standard Apache output mechanisms: ap_rputs(),
* ap_rprintf(), ap_rwrite(), etc.
*
* Each filter is defined by a callback. This callback takes the output from
* the previous filter (or the content generator if there is no previous
* filter), operates on it, and passes the result to the next filter in the
* chain. This pass-off is performed using the ap_fc_* functions, such as
* ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
*
* When content generation is complete, the system will pass an "end of
* stream" marker into the filter chain. The filters will use this to flush
* out any internal state and to detect incomplete syntax (for example, an
* unterminated SSI directive).
*/
/* forward declare the filter type */
typedef struct ap_filter_t ap_filter_t;
/**
* @name Filter callbacks
*
* This function type is used for filter callbacks. It will be passed a
* pointer to "this" filter, and a "bucket" containing the content to be
* filtered.
*
* In filter->ctx, the callback will find its context. This context is
* provided here, so that a filter may be installed multiple times, each
* receiving its own per-install context pointer.
*
* Callbacks are associated with a filter definition, which is specified
* by name. See ap_register_input_filter() and ap_register_output_filter()
* for setting the association between a name for a filter and its
* associated callback (and other information).
*
* The *bucket structure (and all those referenced by ->next and ->prev)
* should be considered "const". The filter is allowed to modify the
* the types and values of the individual buckets should not be altered.
*
* The return value of a filter should be an APR status value.
*
* @ingroup filter
* @{
*/
typedef union ap_filter_func {
/** @} */
/**
* Filters have different types/classifications. These are used to group
* and sort the filters to properly sequence their operation.
*
* The types have a particular sort order, which allows us to insert them
* into the filter chain in a determistic order. Within a particular grouping,
* the ordering is equivalent to the order of calls to ap_add_*_filter().
*/
typedef enum {
/** These filters are used to alter the content that is passed through
* them. Examples are SSI or PHP. */
AP_FTYPE_CONTENT = 10,
/** (XXX somebody rename me or get rid of me please)
* This special type ensures that the HTTP header filter ends up in
* the proper location in the filter chain. */
AP_FTYPE_HTTP_HEADER = 20,
/** These filters implement transport encodings (e.g., chunking). */
AP_FTYPE_TRANSCODE = 30,
/** These filters will alter the content, but in ways that are
* more strongly associated with the connection. Examples are
* splitting * an HTTP connection into multiple requests and
* buffering HTTP * responses across multiple requests.
*
* It is important to note that these types of filters are not
* allowed in a sub-request. A sub-request's output can certainly
* be filtered by ::AP_FTYPE_CONTENT filters, but all of the "final
* processing" is determined by the main request. */
AP_FTYPE_CONNECTION = 40,
/** These filters don't alter the content. They are responsible for
AP_FTYPE_NETWORK = 50
/**
* This is the request-time context structure for an installed filter (in
* the output filter chain). It provides the callback to use for filtering,
* the request this filter is associated with (which is important when
* an output chain also includes sub-request filters), the context for this
*
* Filter callbacks are free to use ->ctx as they please, to store context
* during the filter process. Generally, this is superior over associating
* the state directly with the request. A callback should not change any of
* the other fields.
*/
typedef struct ap_filter_rec_t ap_filter_rec_t;
/**
* This structure is used for recording information about the
* registered filters. It associates a name with the filter's callback
* and filter type.
*
* At the moment, these are simply linked in a chain, so a ->next pointer
* is available.
*/
struct ap_filter_rec_t {
/** The registered name for this filter */
const char *name;
/** The function to call when this filter is invoked. */
/** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
* An AP_FTYPE_CONTENT filter modifies the data based on information
* found in the content. An AP_FTYPE_CONNECTION filter modifies the
* data based on the type of connection.
*/
/** The next filter_rec in the list */
struct ap_filter_rec_t *next;
};
/**
* The representation of a filter chain. Each request has a list
* of these structures which are called in turn to filter the data. Sub
* requests get an exact copy of the main requests filter chain.
*/
struct ap_filter_t {
/** The internal representation of this filter. This includes
* the filter's name, type, and the actual function pointer.
*/
/** A place to store any data associated with the current filter */
void *ctx;
/** The next filter in the chain */
/** The request_rec associated with the current filter. If a sub-request
* adds filters, then the sub-request is the request associated with the
* filter.
*/
request_rec *r;
/** The conn_rec associated with the current filter. This is analogous
* to the request_rec, except that it is used for input filtering.
*/
conn_rec *c;
};
/**
* Get the current bucket brigade from the next filter on the filter
* stack. The filter returns an apr_status_t value. If the bottom-most
* filter doesn't read from the network, then ::AP_NOBODY_READ is returned.
* @param filter The next filter in the chain
* @param bucket The current bucket brigade
* @param mode The way in which the data should be read
* @param block How the operations should be performed
* ::APR_BLOCK_READ, ::APR_NONBLOCK_READ
* @param readbytes How many bytes to read from the next filter.
*/
/**
* Pass the current bucket brigade down to the next filter on the filter
* stack. The filter returns an apr_status_t value. If the bottom-most
* filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned.
* @param filter The next filter in the chain
* @param bucket The current bucket brigade
*/
/**
* This function is used to register an input filter with the system.
* After this registration is performed, then a filter may be added
* into the filter chain by using ap_add_input_filter() and simply
* specifying the name.
*
* @param name The name to attach to the filter function
* @param filter_func The filter function to name
* @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or ::
* AP_FTYPE_CONNECTION
* @see add_input_filter()
*/
/**
* This function is used to register an output filter with the system.
* After this registration is performed, then a filter may be added
* into the filter chain by using ap_add_output_filter() and simply
* specifying the name.
*
* @param name The name to attach to the filter function
* @param filter_func The filter function to name
* @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
* ::AP_FTYPE_CONNECTION
* @see ap_add_output_filter()
*/
/**
* Adds a named filter into the filter chain on the specified request record.
* The filter will be installed with the specified context pointer.
*
* Filters added in this way will always be placed at the end of the filters
* that have the same type (thus, the filters have the same order as the
* calls to ap_add_filter). If the current filter chain contains filters
* from another request, then this filter will be added before those other
* filters.
*
* To re-iterate that last comment. This function is building a FIFO
* list of filters. Take note of that when adding your filter to the chain.
*
* @param name The name of the filter to add
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
* @param c The connection to add the fillter for
*/
request_rec *r, conn_rec *c);
/**
* Variant of ap_add_input_filter() that accepts a registered filter handle
* (as returned by ap_register_input_filter()) rather than a filter name
*
* @param name The filter to add
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
* @param c The connection to add the fillter for
*/
void *ctx,
request_rec *r,
conn_rec *c);
/**
* Add a filter to the current request. Filters are added in a FIFO manner.
* The first filter added will be the first filter called.
* @param name The name of the filter to add
* @param ctx Context data to set in the filter
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
* @param c The connection to add this filter for
*/
request_rec *r, conn_rec *c);
/**
* Variant of ap_add_output_filter() that accepts a registered filter handle
* (as returned by ap_register_output_filter()) rather than a filter name
*
* @param name The filter to add
* @param r The request to add this filter for (or NULL if it isn't associated with a request)
* @param c The connection to add the fillter for
*/
void *ctx,
request_rec *r,
conn_rec *c);
/**
* Remove an input filter from either the request or connection stack
* it is associated with.
* @param f The filter to remove
*/
/**
* Remove an output filter from either the request or connection stack
* it is associated with.
* @param f The filter to remove
*/
/* The next two filters are for abstraction purposes only. They could be
* done away with, but that would require that we break modules if we ever
* want to change our filter registration method. The basic idea, is that
* all filters have a place to store data, the ctx pointer. These functions
* fill out that pointer with a bucket brigade, and retrieve that data on
* the next call. The nice thing about these functions, is that they
* automatically concatenate the bucket brigades together for you. This means
* that if you have already stored a brigade in the filters ctx pointer, then
* when you add more it will be tacked onto the end of that brigade. When
* you retrieve data, if you pass in a bucket brigade to the get function,
* it will append the current brigade onto the one that you are retrieving.
*/
/**
* prepare a bucket brigade to be setaside. If a different brigade was
* set-aside earlier, then the two brigades are concatenated together.
* @param f The current filter
* @param save_to The brigade that was previously set-aside. Regardless, the
* new bucket brigade is returned in this location.
* @param b The bucket brigade to save aside. This brigade is always empty
* on return
* @param p Ensure that all data in the brigade lives as long as this pool
*/
apr_bucket_brigade **b, apr_pool_t *p);
/**
* Flush function for apr_brigade_* calls. This calls ap_pass_brigade
* to flush the brigade if the brigade buffer overflows.
* @param bb The brigade to flush
* @param ctx The filter to pass the brigade to
*/
/**
* Flush the current brigade down the filter stack.
* @param f The current filter
* @param bb The brigade to flush
*/
/**
* Write a buffer for the current filter, buffering if possible.
* @param f the filter doing the writing
* @param bb The brigade to buffer into
* @param data The data to write
* @param nbyte The number of bytes in the data
*/
/**
* Write a buffer for the current filter, buffering if possible.
* @param f the filter doing the writing
* @param bb The brigade to buffer into
* @param str The string to write
*/
/**
* Write a character for the current filter, buffering if possible.
* @param f the filter doing the writing
* @param bb The brigade to buffer into
* @param c The character to write
*/
/**
* Write an unspecified number of strings to the current filter
* @param f the filter doing the writing
* @param bb The brigade to buffer into
* @param ... The strings to write
*/
...);
/**
* Output data to the filter in printf format
* @param f the filter doing the writing
* @param bb The brigade to buffer into
* @param fmt The format string
* @param ... The argumets to use to fill out the format string
*/
const char *fmt,
...)
#ifdef __cplusplus
}
#endif
#endif /* !AP_FILTER_H */